This invention relates to techniques for obtaining radiographic images and, more particularly, to an apparatus and method for obtaining improved radiographic images of opacified anatomy using a fluoroscopic type of equipment in conjunction with a video processor.
A typical x-ray fluoroscopy apparatus includes an x-ray source and an image intensifier which is used to detect the x-radiation. The output of the image intensifier is viewed by a television camera, and the resultant television signal can be presented on a monitor and/or recorded. When a body, such as that of a patient, is interposed between the x-ray source and the detector, x-rays are absorbed in varying degrees depending upon the thickness and composition of different regions of the body. This results in the presentation of a two-dimensional image that can be used, for example, for diagnosing structural abnormalities within the body.
The ability to "see" structure in the body using the described technique depends on the x-ray absorption properties of the structure of interest in relation to the x-ray absorption properties of the material(s) adjacent to the structure. The greater the difference, the greater the "contrast" the structure of interest will have in the resulting television image. The greater the contrast, the greater the clarity of the structure in the image. Consequently, achieving high contrast is a desirable quality with this imaging procedure.
Radiographic contrast agents are used to create a large difference in x-ray absorption behavior where little or none previously existed. For example, blood vessels are virtually invisible on fluoroscopic images (except in the chest) because blood, muscle, fat and soft tissue all possess similar x-ray absorption behavior. Radiographic contrast agents contain material (e.g. air, barium, iodine) which has x-ray absorption properties dissimilar to blood, muscle, fat and the soft tissue. For example, when a bolus of iodinated liquid contrast material is injected into an artery or vein, the vascular structure is given artificially higher contrast on an x-ray image while the contrast material is present within a certain vascular segment. The contrast agent, flowing along with the blood, rapidly washes out of one segment and moves on to the next. In order to outline large segments of vasculature, large boluses of long duration (several second) usually are administered. Since iodinated contrast agents are toxic and present small but significant patient discomfort, as well as some risk of serious complications, only limited quantities are used in common procedures.
It is among the objects of this invention to reduce the amount of contrast material needed for a given procedure, and/or to enhance the image that can be obtained when using a given amount of contrast material. It is a further object hereof to generate improved images of the internal structure of a body.